From publisher blurb:
The Warrens of Zagash is an OSRIC module designed for 6-10 adventurers of Levels 6-8.
The dwarves of these mountains are a good and trustworthy folk, friends to both men and elves dwelling in the region. But their ancient homeland hides many secrets that they might otherwise wish forgotten. Recent rumors have surfaced that a long lost dwarven hall has been discovered. There are whispers that the place was once the center of an evil dwarven cult, though the dwarven authorities will say nothing of it.
A recently acquired treasure map points to an ancient dwarven tunnel complex. Could this be the place? Are these the dangerous halls that were once the home for a dwarven cult worshipping an entity they called the Earth Dragon?